Mercurial > urweb
comparison demo/prose @ 650:fcf0bd3d1667
BatchG demo
| author | Adam Chlipala <adamc@hcoop.net> |
|---|---|
| date | Tue, 10 Mar 2009 16:38:38 -0400 |
| parents | 96ebc6bdb5a0 |
| children | bab524996fca |
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| 649:96ebc6bdb5a0 | 650:fcf0bd3d1667 |
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| 211 <p>Here's an example where client-side code needs to run more code on the server. We maintain a (server-side) SQL sequence. When the user clicks a button, an AJAX request increments the remote sequence and gets the new value.</p> | 211 <p>Here's an example where client-side code needs to run more code on the server. We maintain a (server-side) SQL sequence. When the user clicks a button, an AJAX request increments the remote sequence and gets the new value.</p> |
| 212 | 212 |
| 213 batch.urp | 213 batch.urp |
| 214 | 214 |
| 215 <p>This example shows more of what is possible with mixed client/server code. The application is an editor for a simple database table, where additions of new rows can be batched in the client, before a button is clicked to trigger a mass addition.</p> | 215 <p>This example shows more of what is possible with mixed client/server code. The application is an editor for a simple database table, where additions of new rows can be batched in the client, before a button is clicked to trigger a mass addition.</p> |
| 216 | |
| 217 batchG.urp | |
| 218 | |
| 219 <p>We can redo the last example with a generic component, like we did in the <tt>Crud</tt> examples. The module <tt>BatchFun</tt> is analogous to the <tt>Crud</tt> module. It contains a functor that builds a batching editor, when given a suitable description of a table.</p> | |
| 220 | |
| 221 <p>The signature of the functor is the same as for <tt>Crud</tt>. We change the definition of <tt>colMeta</tt> to reflect the different kinds of column metadata that we need. Each column is still described by a pair of types, and the first element of each pair still gives the SQL type for a column. Now, however, the second type in a pair gives a type of <i>local state</i> to be used in a reactive widget for inputing that column.</p> | |
| 222 | |
| 223 <p>The first three fields of a <tt>colMeta</tt> record are the same as for <tt>Crud</tt>. The rest of the fields are:</p> | |
| 224 <ol> | |
| 225 <li> <tt>NewState</tt>, which allocates some new widget local state</li> | |
| 226 <li> <tt>Widget</tt>, which produces a reactive widget from some state</li> | |
| 227 <li> <tt>ReadState</tt>, which reads the current value of some state to determine which SQL value it encodes</li> | |
| 228 </ol> | |
| 229 | |
| 230 <p><tt>BatchFun.Make</tt> handles the plumbing of allocating the local state, using it to create widgets, and reading the state values when the user clicks "Batch it."</p> | |
| 231 | |
| 232 <p><tt>batchG.ur</tt> contains an example instantiation, which is just as easy to write as in the <tt>Crud1</tt> example.</p> |